Follow Monty Seltz, Service Manager for M&D Distributors, as he troubleshoots a difficult Ford 6.0Liter Diesel compression issue causing one cylinder bank to not fire.

1. Engine Compression in
Ford’s 6.0L Fuel Systems
Causing One Cylinder Bank of Injectors Not to Fire

2. • A Ford 6.0L injector with a defective nozzle tip will allow engine compression to enter the fuel
system. The engine compression enters the fuel system through the injector nozzle’s
pintle/needle when it is not seating/closing correctly. This can be caused by improper installation
of the injector, fuel contamination, or a worn injector. As engine compression enters the fuel
passage in the cylinder head, its higher pressure will push the diesel fuel out of the cylinder head.
This will cause the engine to begin miss-firing in one cylinder first, then all cylinders in the
cylinder bank containing that defective injector.
• Both cylinder heads share a common bore in the fuel filter housing. This common bore supplies
fuel to each cylinder head. Depending on the amount of compression entering the fuel system,
the engine compression could work its way into the opposite cylinder head and cause an engine
stall. The Ford 6.0L engine will idle on four cylinders, however it will not idle on three cylinders.
• For today’s discussion, we are not talking about an incorrectly installed injector with a burnt
nozzle tip and lower O-ring seal. An injector in such a condition has additional symptoms,
including heavy gray-black smoke expulsion, a hydro-locked engine, diesel fuel leaking out of the
exhaust, loud engine knocking, and more.
• The following picture is a classic power balance test display of an engine with a defective injector
nozzle tip that is allowing compression into the fuel system. In this case, injectors 1-3-5-7 are
miss-firing.

3. 1 7 3 5

4. Below is a video of a Ford 6.0L engine running on only one cylinder bank due to engine compression
entering the fuel system through one defective injector.

5. • If you have the above symptoms, the next step is to turn the engine off for around 10 minutes.
This will allow the diesel fuel to return to the cylinder heads. With the key on and using the Ford
IDS scan tool, go to the engine power balance test screen. Now, start the engine and find the first
injector that miss-fires in the miss-firing cylinder bank. This injector will be the one with the
defective injector nozzle tip. Write down this injector’s cylinder number.
• The next step is to verify your diagnostics. Remove the secondary fuel filter and fill the filter
housing with fuel. This is done by turning on and off the ignition switch. When the filter housing is
full, turn off the ignition switch. With the key in the off position, use a starter button and crank
the engine. The next video shows engine compression “bubbles” in the fuel system. If you see
these bubbles, they confirms your diagnostics.
• NOTE: Crank the engine with a starter button and the key in the off position.

6. Fuel Filter Housing - Engine Compression “Bubbles” in the Fuel System – Defective Injector

7. • After confirming your diagnostics, replace the injector that you recorded earlier. After replacing
the defective injector, retest the fuel system before reassembling the engine.
• This is how we test for engine compression in the fuel system. We do not use the standard
balloon test.

8. After replacing the defective injector, retest to confirm the repairs.

9. After reassembling the engine, retest the engine again using the engine power balance test. Then test
drive as normal.
BEFORE REPAIRS AFTER REPLACING ONE INJECTOR

10. Engine After Test Drive and Repairs

11. Thank You
Monty E. Seltz
M&D Distributors
Houston, TX